An In-depth Guide to Chiller Surge

chiller surge causes

Chillers are built to make the best of their abilities to bring high-quality conditions and achieve proper temperature control.

If it is properly maintained and used for its intended purpose, a chiller that has been carefully chosen to meet your needs will not spike. Alterations in the operating conditions can give rise to surges, particularly when the load is light on the system.

A surge could be caused by many maintenance issues, such as clogged tubes, a low refrigerant charge, or non-condensable in the refrigerant itself. It can also be caused by improper management of the water flow rates and condenser water temperatures. Chiller surge low load issues can be addressed or remedied using hot gas bypass or variable frequency drives.

chiller surge explained
what causes a chiller to surge

What is Chiller Surge?

Chillers can be customized to work with various systems and configurations. A properly sized and chosen chiller will not spike if properly maintained and operated within its design limits

A chiller system often has two pressures, one for evaporation (low) and one for condensation (high). The refrigerant is drawn from the low-pressure evaporator by the chiller compressor surge and released into the high-pressure condenser.

Lift is the pressure differential between a compressor's suction and discharge sides. When the compressor pressure differential, or lift, is higher than intended, a phenomenon known as a "chiller surge" occurs, and the refrigerant flows backward from the condenser to the compressor.

The loud, unique, screaming chiller surge sound of a compressor experiencing surge and the corresponding change in amp pull are telltale signs of the surge.

Reasons to protect your chiller from surge conditions?

When it comes to extracting heat from buildings in bulk, chillers are the real workhorses of a district cooling system. Surge is a harmful phenomenon that can occur in chillers if the overall heat transfer process variables deviate from the chiller's design limitations.

What Causes a Chiller to Surge?

Many factors can contribute to chiller surge causes; whether it's a cooling tower or an air-cooled heat exchanger, issues with heat rejection systems are highly prevalent. If the chiller's ability to dissipate heat is impaired, for example, by a blockage or malfunctioning pump, the condenser pressure will rise.

Here are common chiller surging problem:

Fan Problem

Similarly, if there is a problem with the fans or cooling media, the heat rejection system will operate inefficiently, raising the temperature of the return cooling water and, in turn, the pressure in the condenser.

Compressor Problem

Since the compressor is still attempting to pull the refrigerant vapor, the evaporator pressure will drop if there is not enough load or the chilled water return temperature is too low. Too much lift and surge will occur if the condenser pressure is maintained, but the evaporator pressure is too low.

The chiller is a potential additional source of surge. There will be significant lift and surge if the refrigerant level is too low and low evaporator pressure if there is too much non-compressible gas in the refrigerant.

Cold Direct can help you with cost-effective solutions and efficient technicians for chiller repairs.

What is Centrifugal chiller surge?

Compressor components such as the seal, bearings, and blades are all subject to wear and tear due to centrifugal chiller rush. If the compressor can't take it, there could be catastrophic consequences.

The surge will eventually cause chiller damage if nothing is done to prevent it. Most engineers and operators who have worked with centrifugal chillers would attest to the compressor's severe reaction to a surge scenario.

When attempting to minimize lift, how do you go about doing so?

Turn down the lift if you want to protect your chiller from surge; one way to accomplish this is to reduce the temperature of the cooling water returned from the heat rejection system, while another is to increase the temperature of the chilled water left to the process.

If the heat rejection system cannot remove the heat from the cooling water, the management control system may need to raise the existing chilled water setpoint to a higher value. The exact figure relies on the make and type of the chiller.

Alternatively, you could install a variable speed drive on the compressor motor of the chiller to adjust the compressor's speed in light-load situations. Additionally, hot-gas bypass systems can be added to chillers to create a false load on the evaporator by diverting some hot refrigerant vapor from the condenser to the evaporator.

How to Solve Chiller Surge Problems?

However, this can be avoided by installing a VSD (variable speed drive) or VFD (variable frequency drive) on the induction motor that operates the compressor. The compressor's output can then be adjusted by its spinning speed.

Certain chillers have a hot gas bypass to lower capacity while keeping the gas flow through the compressor constant.

Compressors from some manufacturers also come with adjustable diffusers. Maintaining the gas velocity narrows the diffuser gap through which the refrigerant can flow into the volute.

When it comes to Chiller surge problems, we're here and ready to serve you with our perfect Commercial Appliance Repair.


The selection of an appropriate chiller will not produce surge so long as it is well-maintained and used as intended.

Chiller Surge, however, is not only caused by low load situations but also by variations in operating conditions. Pipe scaling, insufficient refrigerant replacement, and lack of refrigerant condensation are all examples of maintenance issues that can lead to surges.

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